Linker: Remove dropTriviallyDeadConstantArrays().

llvm/include/llvm/IR/Module.h

@@ -877,15 +877,6 @@ class LLVM_ABI Module {
   }
 /// @}
 
-  /// Destroy ConstantArrays in LLVMContext if they are not used.
-  /// ConstantArrays constructed during linking can cause quadratic memory
-  /// explosion. Releasing all unused constants can cause a 20% LTO compile-time
-  /// slowdown for a large application.
-  ///
-  /// NOTE: Constants are currently owned by LLVMContext. This can then only
-  /// be called where all uses of the LLVMContext are understood.
-  void dropTriviallyDeadConstantArrays();
-
 /// @name Utility functions for printing and dumping Module objects
 /// @{
 

llvm/lib/IR/LLVMContextImpl.cpp

@@ -147,33 +147,6 @@ LLVMContextImpl::~LLVMContextImpl() {
     delete Pair.second;
 }
 
-void LLVMContextImpl::dropTriviallyDeadConstantArrays() {
-  SmallSetVector<ConstantArray *, 4> WorkList;
-
-  // When ArrayConstants are of substantial size and only a few in them are
-  // dead, starting WorkList with all elements of ArrayConstants can be
-  // wasteful. Instead, starting WorkList with only elements that have empty
-  // uses.
-  for (ConstantArray *C : ArrayConstants)
-    if (C->use_empty())
-      WorkList.insert(C);
-
-  while (!WorkList.empty()) {
-    ConstantArray *C = WorkList.pop_back_val();
-    if (C->use_empty()) {
-      for (const Use &Op : C->operands()) {
-        if (auto *COp = dyn_cast<ConstantArray>(Op))
-          WorkList.insert(COp);
-      }
-      C->destroyConstant();
-    }
-  }
-}
-
-void Module::dropTriviallyDeadConstantArrays() {
-  Context.pImpl->dropTriviallyDeadConstantArrays();
-}
-
 namespace llvm {
 
 /// Make MDOperand transparent for hashing.

llvm/lib/IR/LLVMContextImpl.h

@@ -1808,9 +1808,6 @@ class LLVMContextImpl {
   LLVMContextImpl(LLVMContext &C);
   ~LLVMContextImpl();
 
-  /// Destroy the ConstantArrays if they are not used.
-  void dropTriviallyDeadConstantArrays();
-
   mutable OptPassGate *OPG = nullptr;
 
   /// Access the object which can disable optional passes and individual

llvm/lib/Linker/IRMover.cpp

@@ -1766,7 +1766,5 @@ Error IRMover::move(std::unique_ptr<Module> Src,
   IRLinker TheIRLinker(Composite, SharedMDs, IdentifiedStructTypes,
                        std::move(Src), ValuesToLink, std::move(AddLazyFor),
                        IsPerformingImport);
-  Error E = TheIRLinker.run();
-  Composite.dropTriviallyDeadConstantArrays();
-  return E;
+  return TheIRLinker.run();
 }